PowerPoint has useful tools to align and distribute objects. Spreading things around a circle is more tricky though. Here is one solution that works with an even number of objects circling the center.
  1. Draw the rough configuration of the diagram you want (something in the middle, an even amount of objects around it, not yet aligned)
  2. Align 2 objects horizontally, and fix the distance in between them (left part of the attached illustration)
  3. Using the "size" function copy (in my case I needed 4) them, and rotate them in increments you need (in my case 360/8=45 degrees).
  4. Center and middle-align all objects until the diagram is finished (right section of the attached illustration)